The compound 1,2.2,2-tetrafluoromethyl difuoroethyl ether (CF.sub.3 CHFOCHF.sub.2) is an important volatile liquid inhalation anesthetic particularly suited for administration to patients during outpatient surgery due to its rapid rate of recovery. Economical methods for the preparation of CF.sub.3 CHFOCHF.sub.2 using inexpensive, available raw materials are therefore highly desirable.
One known method for preparing CF3CHFOCHF2 is by first chlorinating 1,2,2,2-tetrafluoroethyl methyl ether (CF.sub.3 CHFOCH.sub.3) to produce a compound having the formula CF.sub.3 CHFOCHCl.sub.2, which compound is then fluorinated with hydrogen fluoride in the presence of antimony pentachloride. See, for example, Ger. Offen. 2,361,058 (1975). However, such a process is disadvantageous for producing CF.sub.3 CHFOCHF.sub.2 on an industrial scale as it is a complex, multiple-step synthesis which can require large amounts of chlorine and is, therefore, both cumbersome and expensive.
The use of hydrogen fluoride with antimony pentachloride as a catalyst as in the above process is nevertheless an attractive method of preparing fluorinated hydrocarbon derivatives such as the subject compound as such well known technology has been used in industry for years and involves inexpensive, readily available raw materials.
U.S. Pat. No. 2,005,708, for example, describes the production of chlorofluoroalkanes from the reaction of a chlorinated hydrocarbon with hydrogen fluoride in the presence of an antimony halide, for example, antimony pentachloride or a mixture of antimony pentachloride and antimony trichloride. U.S. Pat. No. 2,005,705 also describes fluorination of organo chlorine compounds, for example, carbon tetrachloride, methylene chloride, fluorotrichloro methane and the like, with hydrogen fluoride in the presence of an antimony pentachloride catalyst to produce chlorofluoro alkanes. Further, European Application No. 129,863 describes a process whereby antimony pentachloride is first reacted with hydrogen fluoride to produce an antimony chlorofluoride, which is then reacted with a haloalkane, for example, carbon tetrachloride, penta- and hexachloroethane and the like. to produce mixtures of fluoro and chlorofluoroalkanes. None of these references teaches or suggests a means of replacing chloro with fluoro on an internal carbon atom in a chlorofluoro ether containing at least three carbon atoms.
The processes described above, however, have not contemplated the preparation of fluorinated organoethers such as CF.sub.3 CHFOCHF.sub.2. Moreover, the formation of highly fluorinated hydrocarbons by such processes typically involve relatively high reaction temperatures and pressures which, in addition to incurring high energy costs, can cause decomposition of reactants and products and rapid deterioration of process materials.
It is, therefore, an obJect of this invention to provide an economical, energy efficient process employing mild reaction conditions for the preparation of CF.sub.3 CHFOCHF.sub.2 using inexpensive, readily available raw materials.